Embryonic ossification process with the fracture callus formation

      Embryonic ossification process with the fracture callus formation and ectopic bone formation process is similar to, and are subject to the regulation of certain hormones and local growth factor body. Generally believed, parathyroid hormone (PTH), growth hormone, thyroxine, calcitonin, estrogen hormones affect bone tissue formation; mainly of BMPs local growth factors affect bone tissue formation, transfer factor (TGF) platelet-derived growth factor (PDGF), insulin-like growth factors (IGFs), interleukin (ILs). In the process of bone tissue formation, between hormones and growth factors regulating both relative independence, and mutual contact. Two regulatory nervous system together form a nerve – endocrine – immune – local growth factor regulatory networks involved in the formation of bone tissue throughout the adjustment process. Is generally believed that the local growth factor plays a dominant role in the regulation of bone formation process. Especially BMPs is the only one able to alone induced differentiation of mesenchymal cells to the direction of the bone tissue growth factor, is the most critical regulatory factor in the process of bone tissue formation. The experiments show that the low concentrations of BMPs able to induce mesenchymal cells into bone tissue formation region transitional; the medium concentration BMPs can promote mesenchymal cells to differentiate into chondrocytes and osteoblasts direction; while high concentrations of BMPs into mesenchymal cells can promote proliferation. The study, BMP-2, the main role of the recruitment and differentiation of undifferentiated mesenchymal cells and bone lineage cells play. In early bone formation, BMP-2 can undifferentiated mesenchymal cells to bone form the center raised and differentiate into bone lineage cells, but also enable the fibroblasts, myoblasts and bone marrow reversal of basal cell differentiation to bone lineage cells . The main process is to: increase or inhibit the secretion of certain specific proteins within these cells, fibroblasts differentiate into osteoblasts, myoblasts quick to differentiate into cartilage cells hypertrophy, and promote matrix calcification. For osteoblasts, BMP-2 can maintain their unique cell phenotype, and the induction increased markers of bone cells and promoting the calcification of the extracellular matrix. In the late stage of bone formation, BMP-2 as an osteoclast cell differentiation factor, and other support osteoclast differentiation factor, either directly or indirectly, to stimulate osteoclast differentiation involved in bone reconstruction. BMP-2 whether to promote cell mitosis and replication role, are still controversial. But to be sure, in promoting cell mitosis and replication process, BMP-2 and other local factors have a synergistic effect. Therefore, the formation of bone tissue is co-regulated by a variety of local factors.

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